Synthesis Of Organic Osmolytes Research Articles

Metabolomic pattern associated with physical sequelae in patients presenting with respiratory symptoms validates the aestivation concept in dehydrated patients.

Hypertonic dehydration is associated with muscle wasting and synthesis of organic osmolytes. We recently showed a metabolic shift to amino acid production and urea cycle activation in coronavirus-2019 (COVID-19), consistent with the aestivation response. The aim of the present investigation was to validate the metabolic shift and development of long-term physical outcomes in the non-COVID cohort of the Biobanque Québécoise de la COVID-19 (BQC19). We included 824 patients from BQC19, where 571 patients had data of dehydration in the form of estimated osmolality (eOSM = 2Na + 2K + glucose + urea), and 284 patients had metabolome data and long-term follow-up. We correlated the degree of dehydration to mortality, invasive mechanical ventilation, acute kidney injury, and long-term symptoms. As found in the COVID cohort, higher eOSM correlated with a higher proportion of urea and glucose of total eOSM, and an enrichment of amino acids compared with other metabolites. Sex-stratified analysis indicated that women may show a weaker aestivation response. More severe dehydration was associated with mortality, invasive mechanical ventilation, and acute kidney injury during the acute illness. Importantly, more severe dehydration was associated with physical long-term symptoms but not mental long-term symptoms after adjustment for age, sex, and disease severity. Patients with water deficit in the form of increased eOSM tend to have more severe disease and experience more physical symptoms after an acute episode of care. This is associated with amino acid and urea production, indicating dehydration-induced muscle wasting.NEW & NOTEWORTHY We have previously shown that humans exhibit an aestivation-like response where dehydration leads to a metabolic shift to urea synthesis, which is associated with long-term weakness indicating muscle wasting. In the present study, we validate this response in a new cohort and present a deeper metabolomic analysis and pathway analysis. Finally, we present a sex-stratified analysis suggesting weaker aestivation in women. However, women show less dehydration, so the association warrants further study.

Recovery from Salinity and Drought Stress in the Perennial Sarcocornia fruticosa vs. the Annual Salicornia europaea and S. veneta.

Current agricultural problems, such as the decline of freshwater and fertile land, foster saline agriculture development. Salicornia and Sarcocornia species, with a long history of human consumption, are ideal models for developing halophyte crops. A greenhouse experiment was set up to compare the response of the perennial Sarcocornia fruticosa and the two annual Salicornia europaea and S. veneta to 30 days of salt stress (watering with 700 mM NaCl) and water deficit (complete withholding of irrigation) separate treatments, followed by 15 days of recovery. The three species showed high tolerance to salt stress, based on the accumulation of ions (Na+, Cl−, Ca2+) in the shoots and the synthesis of organic osmolytes. These defence mechanisms were partly constitutive, as active ion transport to the shoots and high levels of glycine betaine were also observed in non-stressed plants. The three halophytes were sensitive to water stress, albeit S. fruticosa to a lesser extent. In fact, S. fruticosa showed a lower reduction in shoot fresh weight than S. europaea or S. veneta, no degradation of photosynthetic pigments, a significant increase in glycine betaine contents, and full recovery after the water stress treatment. The observed differences could be due to a better adaptation of S. fruticosa to a drier natural habitat, as compared to the two Salicornia species. However, a more gradual stress-induced senescence in the perennial S. fruticosa may contribute to greater drought tolerance in this species.

Expressing Arabidopsis thaliana V-ATPase subunit C in barley (Hordeum vulgare) improves plant performance under saline condition by enabling better osmotic adjustment.

Salinity is a global problem affecting agriculture that results in an estimated US$27 billion loss in revenue per year. Overexpression of vacuolar ATPase subunits has been shown to be beneficial in improving plant performance under saline conditions. Most studies, however, have not shown whether overexpression of genes encoding ATPase subunits results in improvements in grain yield, and have not investigated the physiological mechanisms behind the improvement in plant growth. In this study, we constitutively expressed Arabidopsis Vacuolar ATPase subunit C (AtVHA-C) in barley. Transgenic plants were assessed for agronomical and physiological characteristics, such as fresh and dry biomass, leaf pigment content, stomatal conductance, grain yield, and leaf Na+ and K+ concentration, when grown in either 0 or 300mM NaCl. When compared with non-transformed barley, AtVHA-C expressing barley lines had a smaller reduction in both biomass and grain yield under salinity stress. The transgenic lines accumulated Na+ and K+ in leaves for osmotic adjustment. This in turn saves energy consumed in the synthesis of organic osmolytes that otherwise would be needed for osmotic adjustment.

Eco-physiological adaptations of Panicum antidotale to hyperosmotic salinity: Water and ion relations and anti-oxidant feedback

Threshold of salt resistance of plants is determined by their response to osmotic and ionic stress (primary constraints) imposed upon them. However, recent reports emphasize the importance of secondary constraints like oxidative stress. The aim of this study was to determine the effect of salinity on growth, mineral nutrition, water relations, compatible solutes, and the antioxidant system in Panicum antidotale.Five levels of salinity (0, 125, 250, 375 and 500mM NaCl) were applied using a quick check system in a fully randomized greenhouse study. Plant growth parameters, water relations, organic (proline and soluble sugars), inorganic osmolytes (Na+, K+, Ca++and Mg++), and macronutrients such as carbon or nitrogen were measured beside the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APx) and glutathione reductase (GR) and non-enzymatic antioxidant metabolites (oxidized and reduced ascorbate).Sodium chloride concentrations above 125mM substantially inhibited growth. This inhibition was attributed to high energy costs needed for osmotic adjustment, ion compartmentalization, synthesis of organic osmolytes (such as proline and sugars), ROS scavenging and the maintenance of ionic homeostasis. The plants resisted against oxidative stress by increasing activities of antioxidant enzymes such as SOD, APx, GR and CAT and elevating levels of oxidized and reduced ascorbate (DAsA and AsA) at higher salinity. They also maintained a low redox ratio of ascorbate/dehydro-ascorbate and therefore a high capacity to manage oxidative stress. Thus P. antidotale is capable of managing ROS stress at high salinity and therefore can be sustainably grown as a fodder crop in saline arid regions.

Synthesis of organic osmolytes and salt tolerance mechanisms in Paspalum vaginatum

Synthesis of organic compounds in response to salinity stress and their contribution to organic osmotic adjustment were investigated in seashore paspalum ( Paspalum vaginatum Swartz). Nine genotypes exhibiting the widest range of salt tolerance were grown in sea-salt amended nutrient solution in a greenhouse. Salinity ranges were 1.1 (EC w0, control) to 49.7 dS m −1 (EC w50) based on electrical conductivity of the solution (EC w). Organic osmolytes most important within seashore paspalum under salinity stress were proline, Gly-betaine, and trigonelline in terms of explaining intraspecific salt tolerance differences and, therefore, should be the focus of biotechnology approaches to enhance these traits. While these osmolytes differed in accumulation with increasing salinity and absolute concentrations among salt tolerant and intolerant genotypes, the magnitude of responses was not sufficiently large to suggest use for salt screening as physiological/biochemical markers. Fructose concentration increased with salinity, especially for salt sensitive ecotypes, and may have potential as a marker. Glucose, sucrose, and myo-inositol tended to increase with salinity, but changes did not relate to intraspecific salt tolerance, while mannitol and sorbitol were not affected by salinity. Proline demonstrated a 20.8-fold increase averaged across genotypes from EC w0 to EC w50 salinity. Proline was the primary organic osmolyte for osmotic adjustment accounting for an average of 9.3% to total solute potential ( Ψ s) at EC w50 and 56% of the organic solute contribution to Ψ s. In the salt tolerant genotype, SI 93-2, proline and Gly-betaine exhibited greater absolute concentration and accumulation rate relative to the least salt tolerant, Adalayd. The intraspecific role of Gly-betaine did not relate to osmotic adjustment differences, suggesting another role perhaps in protection of the thylakoid membrane.

Restoration of urine concentrating ability and accumulation of medullary osmolytes after chronic diuresis.

Restoration of urine osmolality (Uosm) and medullary osmolyte contents after chronic diuresis was studied in rats infused for 6 days with furosemide and subsequently given the vasopressin analogue, 1-desamino-8-D-arginine vasopressin (DDAVP). Papillary tip intra- and extracellular electrolyte concentrations were measured by electron microprobe analysis, tissue contents of methylamines (glycerophosphorylcholine, betaine), polyols (myo-inositol, sorbitol), and several amino acids in different kidney zones by high-performance liquid chromatography. Administering DDAVP continuously after diuresis increased Uosm from (means +/- SE) 348 +/- 8 to 1,265 +/- 127 after 1 day and 2,485 +/- 186 mosmol/kgH2O after 3 days. The sum of all osmolytes at the papillary tip rose from 309.2 +/- 28.9 to 690.9 +/- 105.8 and 1,282.8 +/- 21.0 mmol/kg protein after days 1 and 3, respectively. Although interstitial tonicity (sum of Na, Cl, and K concentrations) was increased by 116 and 223% after 1 and 3 days DDAVP, intracellular tonicity was similar in chronic diuresis and following 1 or 3 days DDAVP. Coadministration of DDAVP with betaine, myo-inositol, and choline ("osmolyte treatment") did not accelerate the restoration of Uosm but caused significantly higher contents of osmolytes (except myo-inositol) in inner medulla and/or papilla after 3 days. In a minority of animals, restoration of Uosm and reaccumulation of medullary osmolytes were impeded in both DDAVP- and DDAVP/osmolyte-treated rats. These data indicate that, after chronic diuresis, accumulation of organic osmolytes and restoration of Uosm proceed in parallel. Capacity for transport and/or synthesis of organic osmolytes, rather than their availability, appear to limit reaccumulation on the first day of recovery. By the third day, delivery of some osmolytes or their precursors may limit the restoration of medullary osmolyte content. The failure of some rats to attain sufficient concentrating ability within this time period may be related to deficient reaccumulation of medullary osmolytes.